2020/16

dlx/include/dlx.hpp

@@ -4,6 +4,7 @@
 #include <cstddef>
 #include <functional>
 #include <vector>
+#include <utility>
 
 namespace dlx {
 
@@ -39,8 +40,8 @@ public:
   // Increases the number of rows and columns if necessary.
   auto Set(std::size_t row, std::size_t col) -> void;
 
-// Marks a column as optional: a solution need not cover the given column,
-// but it still must respect the constraints it entails.
+  // Marks a column as optional: a solution need not cover the given column,
+  // but it still must respect the constraints it entails.
   auto MarkOptional(std::size_t col) -> void;
 
   // Removes a row from consideration.
@@ -53,19 +54,19 @@ public:
   auto PickRow(std::size_t row) -> void;
 
   auto Solve(
-    std::function<void(std::size_t, std::size_t, std::size_t)> try_cb,
-    std::function<void()> undo_cb,
-    std::function<void()> found_cb,
-    std::function<void(std::size_t)> stuck_cb) -> void;
+    std::function<bool(std::size_t, std::size_t, std::size_t)> try_cb,
+    std::function<bool()> undo_cb,
+    std::function<bool()> found_cb,
+    std::function<bool(std::size_t)> stuck_cb) -> void;
 };
 
 auto ForallCover(Dlx& dlx, auto cb) {
   std::vector<std::size_t> sol;
   dlx.Solve(
-    [&](std::size_t c, std::size_t s, std::size_t r) { sol.push_back(r); },
-    [&](){ sol.pop_back(); },
-    [&](){ cb(sol); },
-    [](std::size_t){}
+    [&](std::size_t c, std::size_t s, std::size_t r) { sol.push_back(r); return false; },
+    [&](){ sol.pop_back(); return false; },
+    [&](){ return cb(std::as_const(sol)); },
+    [](std::size_t){ return false; }
   );
 }